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| Home > Publications database > Thermomechanisches Verhalten gefügter Divertormodule unter fusionsrelevanten Belastungen |
| Book/Report | FZJ-2018-06838 |
; ;
1994
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
Jülich
Please use a persistent id in citations: http://hdl.handle.net/2128/20203
Report No.: Juel-2933
Abstract: In the present work the thermomechanical behaviour of four single-tube divertor modules and a prototypical divertor plate under heat fluxes, which are expected for future fusion reactors as NET or ITER, has been characterized. The specimens were made up of a heat sink of the molybdenum-alloy TZM with a cooling tube of Mo41Re and armour tiles of multi-directional carbon fibre reinforced carbon material (CFC) brazed to the heat flux facing side. Two different designs (with and without a TZM-mterlayer between CFC-tile and heat sink, respectively) were investigated. The prototype consisted of 8 cooling channels connected by collectors. The specimens were exposed both to stepwise increasing as well as to cyclic heat loads in an ion beam facility with hydrogen and helium beam, respectively, and in two electron beam machines (scanned and stationary beam, respectively) with pulse lengths allowing quasistationary thermal conditions to be achieved. Whereas in the electron beam tests the divertor modules resisted up to 20.7 MW/m$^{2}$ in a single pulse and up to 15 MW/m$^{2}$ under cyclic loading (300 cycles) without failure, damage occurred at significantly lower heat fluxes and already after few pulses in the ion beam experiments. As an explanation for the different behaviour embrittlement of the zirconium high temperature braze between CFC and heat sink under the influence of the hydrogen ion beam was found. Thermal loading results in high vertical temperature gradients during the transient as well as the stationary phases, causing bending of the armour tiles. Thus high stresses in the bonding zones arise, which can lead to detachment of the tiles. This damage mechanism could be observed in the experiments and was confirmed by numerical analyses of the resulting temperature and stress fields by using a finite-element- code. The early failure of the divertor prototype could be attributed to unfavourableorientation of the CFC-tiles, melting of the brazed joints caused by heat absorption in the gaps between the armour tiles and deteriorated cooling efficiency.
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